Two decades ago, X-Files composer Mark Snow produced a compilation dubbed Songs in the Key of X: Music From and Inspired by the X-Filesthat included tunes by Nick Cave, Elvis Costello, P.M. Dawn and William S. Burroughs with R.E.M., among others. It also contained a cover of Gary Numan’s echoey, new-wavey “Down in the Park” by some alt-rock upstarts calling themselves Foo Fighters, whose frontman was an X-Files megafan. That same year, he got the chance to appear on the show.

“Dave Grohl was a big fan of the show,” Gillian Anderson tells Rolling Stone with a laugh. “He came to the set for one episode as an extra. He did a cameo; a drive-by. If you blink, you miss him. He ended up just being the guy in a hallway.”

The episode, “Pusher,” aired 20 years ago this week on February 23rd, 1996, and focused on Scully and Mulder hunting down a man who could subliminally command people to do his bidding. Grohl’s scene appears in the FBI building, as the man with mind-control powers sneaks in; the Foo Fighter is seen with his then-wife Jennifer Youngblood. Two years later, Grohl and his Foo Fighters bandmates re-recorded the Colour and the Shape track “Walking After You” for The X-Files: The Album, which came out in 1998 as the soundtrack to the X-Files movie.

“I was obsessed with The X-Files,” Grohl told Anderson in 2014 on the BBC program The One Show. “I don’t want to scare you, but I was an obsessive fan.” He later expounded on his infatuation with the show in an interview with BBC Radio 1, via music-news.com. “[Gillian] was the one person who I was like, ‘We’re gonna get married. One of these days, she and I will finally meet and this will finally happen,'” he said. “So last night, I was just sitting next to her like, [whispers] ‘It’s Gillian Anderson, Oh, my God.’ I don’t even know what I said or how I answered the questions; I was just looking at her like, ‘She’s so beautiful.'”

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In her Rolling Stone interview, which will run in full tomorrow to follow tonight’s season finale, Anderson also revealed other musicians who were X-Files diehards. “The Smashing Pumpkins were big fans, too,” she says. “Their lead singer, Billy Corgan, used to come and hang out on set. And Chris Martin is a fan. Whenever they were in town, his manager dragged him to our set. So yeah, we’ve got a good relationship with some rockers.”

As for the Songs in the Key of X comp, Anderson would like to hear what musicians offered now. “I think we should do that again if we ever do more episodes,” she says. “You could still ask Nick [Cave] to do it, and I think there’s a new version of that Catatonia song, ‘Mulder and Scully.’ And there’s a new video for [Bree Sharp’s] ‘Why Won’t You Love Me, David Duchovny?’“